The aim of the proposed project is to obtain basic information on the site and mechanism of synthesis of the major surface active components of pulmonary surfactant - the phospholipids dipalnitoylglycerophosphocholine and phosphatidylglycerol. In particular the role of the alveolar type II cell and lamellar body fraction in the synthesis of phosphatidylcholine and phosphatidylglycerol will be established. Synthesis of disaturated phosphatidylcholine by deacylation and reacylation pathways will be examined. The lipid composition of fetal rabbit lung wash and lung tissue as well as the activities of enzymes of pulmonary phospholipid synthesis will be determined following administration of betamethasone and thyrotropin releasing hormone to the doe in order to elucidate the mechanism of surfactant synthesis and its control by hormones during fetal development. These studies are of clinical importance since immaturity of the lung with insufficient surfactant is believed to be the cause of respiratory distress syndrome of the newborn - the major cause of morbidity and mortality among premature infants in the United States. BIBLIOGRAPHIC REFERENCES: S.A. Rooney, L.L. Nardone, D.L. Shapiro, E.K. Motoyama, L. Gobran and N. Zaehringer: The phospholipids of type II alveolar epithelial cells: Comparison with lung lavage, lung tissue, alveolar macrophages, and a human alveolar tumor cell line. Lipids. 12: 438-442, 1977. S.A. Rooney: Phospholipid content of lung lavage in the newborn rabbit. Fed. Proc. 36: 790, 1977.